SC-68420 is a genetically engineered molecule which combines interleukin-3 (IL-3) and G-CSF receptor agonist activities. SC-68420 is composed of a genetically engineered rhIL-3, (SC-55494, an agent currently in Phase I/II clinical trials), a linker composed of glycine and serine amino acids, and a genetic variant of G-CSF. The resulting structure binds to the human G-CSF and human IL-3 receptors with high affinity. The development of SC-68420 was prompted by in vivo and vitro findings showing synergy between the two growth factors. SC-68420 demonstrates a significant improvement in stimulating hematopoiesis in vitro and in vivo relative to rhIL-3 given concurrently with recombinant human granulocyte colony stimulating factor (rhG-CSF). The primary clinical application for SC-68420 is bone marrow regenerative therapy in cancer patients receiving myelosuppressive chemotherapy (CT). Clinical studies of SC-68420 are currently being conducted in HDCT settings since SC-68420 is expected to optimize neutrophil recovery, stimulate platelet recovery, and mobilize hematopoietic progenitors into the peripheral blood.